Distribution coefficients of iodine and tin on granodiorite and tuffaceous sandstone specimens

Abstract

  Iodine and tin are important elements in performance assessment of geological disposal of radioactive wastes. Sorption experiments of iodine were carried out under varying nitrate concentration with a range of 0 to 5 mol dm^-3 at neutral pH range in order to determine the distribution coefficient of iodine was zero or non-zero value. The experimental results with estimated statistical errors showed non-zero values for tuffaceous sandstone except for NaNO₃ concentration 0.5 mol dm^-3. Non-zero values were also obtained under NaNO₃ concentrations higher than 0.5 mol dm^-3 for granodiorite. Sorption experiments of tin were carried out at high pH range in order to check whether the distribution coefficient of tin decreases significantly with pH as a result of formation of anionic hydrolysis species of tin. The distribution coefficients of tin on granodiorite decreased from 9.79×10^-2 m³ kg^-1 at pH 10.4 to 2.46×10^-3 m³ kg^-1 at pH 12.4. The distribution coefficient of tin on tuffaceous sandstone was about one order of magnitude higher (about 2×10^-2 m³ kg^-1) than that of granodiorite at pH around 12.4.